Electric starter motors can be used to initiate piston motion in an internal combustion engine before combustion alone can reliably reciprocate the pistons. Some starter motors are controlled by a starter motor relay having a low side that is controlled by a powertrain control module, and a high side powered directly through the ignition key circuit. Once the engine starts, the powertrain control module disables the low side of the starter relay, which turns the starter motor off.
The inventors herein have recognized several issues with this approach. In particular, the crank duration is limited by how long the operator keeps the ignition key at a START position. If the key is released prematurely, the result may be excessive fuel in the cylinders, extended engine cranks, and/or potentially rough engine starts.
Another type of an electric starter motor is described in U.S. Pat. No. 6,481,404. In this example, a starter relay is also used to turn the starter motor on and off. However, the starter relay is connected to controllers that make all decisions as to when the starter motor is to be turned on and off.
The inventors herein have recognized several issues with this approach. In particular, once an operator initiates an engine startup, all control is taken away from the operator. This can produce unsatisfying operator feedback, and does not allow an operator to override decisions made by the controllers.
In one embodiment, the above issues may be addressed by a starter control system that includes a starter relay that is independently controllable by a control module and an ignition switch. The starter relay includes a high side node and a low side node and is controllable to selectively enable power delivery from a power source to a starter motor responsive to activation of the high side node and the low side node. The starter control system also includes a control module including a high side driver in operative communication with the high side node of the starter relay and a low side driver in operative communication with the low side node of the starter relay. Furthermore, the starter control system includes an ignition switch in operative communication with the high side node of the starter relay and in operative communication with the control module. Such an arrangement allows the high side node to be automatically turned on via the control module, or manually turned on directly via the ignition switch.